Remove helper methods that were moved to helper.rb

Signed-off-by: José Valim <jose.valim@gmail.com>

activerecord/test/cases/base_test.rb

@@ -1433,19 +1433,4 @@ def test_default_scope_is_reset
   ensure
     Object.class_eval{ remove_const :UnloadablePost } if defined?(UnloadablePost)
   end
-
-  protected
-    def with_env_tz(new_tz = 'US/Eastern')
-      old_tz, ENV['TZ'] = ENV['TZ'], new_tz
-      yield
-    ensure
-      old_tz ? ENV['TZ'] = old_tz : ENV.delete('TZ')
-    end
-
-    def with_active_record_default_timezone(zone)
-      old_zone, ActiveRecord::Base.default_timezone = ActiveRecord::Base.default_timezone, zone
-      yield
-    ensure
-      ActiveRecord::Base.default_timezone = old_zone
-    end
 end